Oxygen purity improvement method and apparatus



March 1954 s. c. COLLINS ET AL OXYGEN PURITY IMPROVEMENT METHOD AND APPARATUS Filed Dec. 28 1949 3 Sheets-Sheet 1 w n w m Jamaal CC'OZZ z Zdwz Z1]. Faye! Lewuls Tyree attorney.

March 1954 s. c. COLLINS ET AL 2,6 1,3

OXYGEN PURITY IMPROVEMENT METHOD AND APPARATUS Filed Dec. 28, 1949 I5 Sheets-Sheet 2 attorney.

March 9, 1954 s. c. COLLINS ET AL OXYGEN PURITY IMPROVEMENT METHOD AND APPARATUS 3 Sheets-Sheet 3 Filed Dec. 28 1949 Patented Mar. 9, 1954 UNITED STATES FATENT OFFICE OXYGEN PURITY IMPROVEMENT- METHOD- AND APPARATUS Pennsylvania Application December 28, 1949, Serial No. 135,462

17 Claims.

Gur invention relates to improvements in methods of and means for treating gases. It will be described particularly in its application to production of substantially pure'oxygenirom air, but this is butillustrative because the process and apparatus' disclosed may-be used, with appropriate modifications, with-various gases to be processed, to produce various particularly desired products whichjareconstituents of the gases to be treated.

Fol-"many uses it is importantthat' the purity of the oxygen-delivered by anoxygen generator shall bemaintainedat'a high value, as 99.5%. With generators whichproduceoxygen by the separation of atmospheric air itis at times difiicultto maintain thishigh degree of. product purity, and itiis' important that there shall be provided means for-improving the purity whenitfalls below. the. required'standard. It is also important that such improvement efiecting means be automatically controll'edand highly desirable. that it be controlled'by the. purity of the product itself.

Aneffective way of improving the product purity,,we have discoveredis to deliver to the bottom or the. column,,when.a single column is used, or to..an appropriate point whena multiple column is employed, a quantity ofthe oxygen product; This may berelatively warm oxygen from an,out side source, or may. be oxygen from. any point where asuiiicient. pressure existsin the generating,system,.between the pointof withdrawal of theoxygenfrom .the. column and its pointoidischarge.fromthesystem. When a liquid oxygen. pumpis used to raisethe. pressure or. the oxygen withdrawnironi the columnany point between the pump dis harge. and the. point offinal. discharge-fromthe. system may. be selected. The cationof. the point selectedwill, however, affect. the. respective contributions to purityimprove- 111810111 made by the dififerent factorswhich may playapart.

The rate at whichthe gaseous oxygen rises in the-column markedly. afiects the purity of the cxygenproduct, and when relatively warm gaseous, oxygen is released to the bottom of the column; speaking here of a single column, the gas rate. wilLbe markedly. increased. The heat will. boil the liquid-oxygenmore rapidly-increasing the gas-flow up-the. column. Inaddition the actual volume of gas going. up. the column will :be inscreased bythe. returned oxygen;

While; it is; considered preferable to: introduce; the warmerroxygen;beneath-the top of; this-liquid iintheecoiumng its introduction between ;the:liquid level :anchthe; bottom ;ofi th ezpacking :iscwithinzthe; hmadenaspects, off: oiurinvention: K115311013 tonbeir understood that our invention is limited, however; to-the introduction of warrner oxygen-ox-ygen warmer than the temperature at its point ofintroductionor to the introduction of oxygen either below the level of liquid oxygen in-the column, or at apoint below the bottom of tlie packing. Nor is the invention limited to the-production of 1 oxygen.

A point to remember inapproaching the--invention is that thetemperature of the liquid descending through the column isa functionof the compositionof the liquid; and gets lower as the per cent of oxygen is reduced? In other words, the less pure the liquid passing to'the bottom of the column, thecolderthe liquidwhich passes to the-bottom of'the column; Thisphenomenon We have taken advantage of" to provide an automatic controlofthe rate of oxygenreturn to; the bottom of the column,- through the use of the differential between the saturatedvapor-pres sure ofaquantity ofsubstantially pure oxygenina closed'system at the temperature-at apoihtat which purity control. is; desired, andmthe pressure subsisting in'the column" at such point; As-Will later. appear,- the purity ofxtheoxygen'in the auto;- matic control-system may be higher or'lower-than the desired'product purity; It willQbe understood that. in the. separation of some substances from some mixtures an opposite temperature. change takes place with decreasing product purity, and under such conditions useis still made of'thedifferential betweenthe saturated'vapor pressure of; aquantity, in relatively pure form, of a substance whose purity is .to be controlled, at the temperature of a pointat which purity control is to be of fected, and .the pressure at such point'in the fractionating apparatus.

It is an objectof our invention to providean improved'method of producing oxygen of high purity. Itisanother objectlof our inventionto provide an. improved apparatus. for producing. oxygen of, high purity, having automaticmeans for insuring the maintenance. ofthe desired. high, degreeoipurity. It is. a further objectof-ourin.-

vention to provide an improved automatic controlj means for. an oxygen generating apparatus for;

maintaining a highdegreesof purity-0f the. product. thereof. It.is,.sti1l another object. of our-in:- vention to provide an improved method of treate ing atmospheric air for the-purpose of-producing.

oxygenoi high purity and includingthe step-of:

warmed portion of the leaving oxygen product, so that by increasing the rate of boiling in the column the rectification process may be improved. It is yet a further object to provide an improved method of regulating an oxygen purity control apparatus. It is still another object of the invention to provide an improved method of improving an end product of a rectification process involving the delivery to an appropriate point in a column of a quantity of warmer gas corresponding generally in constitution to said end product, and automatically controlling the quantity delivered in direct proportion to the deviation of such product from a desired degree of purity. Other objects and advantages of my invention will hereinafter more fully appear.

In the accompanying drawing, in which a single column apparatus embodiment of the invention and a modification are shown for the purpose of illustrating the invention from its apparatus aspect and disclosing the practice of its method aspect,

Fig. 1 is a diagrammatic view of an oxygen generating apparatus having our improved purity control incorporated therein in its illustrative form.

Fig. 2 is a much enlarged view, partially in section and with parts broken away illustrating details of the automatic control apparatus in a preferred form.

Figs. 3 and 4 are further enlarged detail sectional views, respectively on the planes of the section lines 3-3 and 4-4 of Fig. 2, Fig. 4 being partially broken away to a still lower plane, and

Fig. 5 is a view similar to Fig. 2 showing a modifled construction.

For the purpose of illustrating our invention we have shown it incorporated in an oxygen generating system which in many respects is closely similar to the system shown in the Samuel C. Collins application Serial No. 383,541, filed October 1, 1953, which is a division of now abandoned application Serial No. 122,077, filed October 18, 1949, for Methods of and Means for Treating Gases. According to that system, air at a temperature of approximately 300 K. and a pressure on the order of 160 p. s. i. (all pressures are gauge unless otherwise indicated) may be delivered from a suitable air compressor (not shown) through a conduit to a valve mechanism generally designated 2, and the effluent (mainly nitrogen) leaving the apparatus may be discharged to the atmosphere or some other desired point through a conduit IS. The valve mechanism I2 is of the mechanically actuated type and is periodically shifted by power, and with a snap action, to reverse the connections of the conduits II and 3 with a pair of conduits 5 and I6 which lead from the casing of the valve mechanism l2. Machanism suitable for this purpose forms the subject matter of an application of Win W. Paget, Serial No. 35,092, filed June 25, 1948, and now Patent 2,638,923. The power for shifting the valve mechanism l2 to effect connection of the air supply conduit now with the conduit I5 and again with the conduit H5, and connection of the conduit l3 with the conduits H and I5 while the conduit I is connected with the conduits l5 and I6, may be taken from any suitable source, such as the drive shaft of an expansion engine It, through any suitable reducing gearing. Reversals are adapted to be eifected at relatively short intervals; and suitable intervals may be on the order of 3 minutes. Heat exchangers 2| and 22, desirably vertically disposed and formed as separate units instead of as one longer unit, in order to keep height within desirable limits, are arranged in series, and entering air passes through the heat exchangers 2| and 22 in the order mentioned, while leaving nitrogen passes through these same units in the order 22, 2|. Exchanger 2| has three courses, indicated as ooaxial courses 2|A, 2|B and 2|C, the first the innermost course and the latter the outermost. The exchanger 22 has similarly relatively arranged courses 22A, 22B and 22C, and, outside the course 220, a fourth course 22D. Through two of the courses in series in the exchangers 2| and 22, namely courses 2 l3, 22B and courses 2 C, 220, the entering air and leaving nitrogen flow alternately, the entering air flowing inwardly through one or the other of these pairs of courses and the nitrogen flowing outwardly through the one of such pairs of courses not at any given moment serving for the inflow of the air. Through the third courses 2| A of the exchanger 2| and 22A of the exchanger 22, but in the order 22A, 2|A, the leaving oxygen product is discharged from the generator. Through the fourth course 22D of the exchanger 22 a portion of the I air on its way to the column is caused, after leaving the exchanger 22, to re-circulate through the latter, the better to effect the depositing out of impurities from the entering air stream in the exchanger 22 and their later sublimation and removal from that exchanger, and to increase the temperature of the air entering the expansion engine.

It has been voted with respect to the exchangers 2| and 22, and it will be noted, with respect to further heat exchangers 23 and 24 hereinafter to be described, that the courses are indicated as being coaxial. This is for simplicity of illustration and it will be appreciated that the construction of these heat exchangers may assume various forms. However, exchanger 23 will be observed shortly to be of the four-course type, and exchanger 24 of the three-course type. Subject to these characteristics, it will be understood that a wide range of difierent constructions may be employed.

Conduit |5 communicates with course 2IB of exchanger 2| and conduit IS with course 2|C of exchanger 2|, and the leaving oxygen passes outwardly through course 2|A of exchanger 2| and passes to a connection S which may lead to a shop line, to a bank of cylinders or to any other desired point or apparatus, for use or storage. Course 2|C of exchanger 2| is connected by a conduit 3| with course 22C of exchanger 22. Course ZIB of exchanger 2| is connected by a conduit 32 with course 22B of exchanger 22. A conduit 33 connects course 2|A of exchanger 2| with course 22A of exchanger 22. These courses are traversed serially in the order 22A, 2 IA by the oxygen product as later described. It will be understood that air will flow alternately in through course 2 |C, conduit 3|, and course 22C, or course 2|B, conduit 32 and course 22B, while concurrently nitrogen will flow outwardly through the ones of said courses and passages last mentioned not carrying the entering air.

A suitable automatic reversing valve mechanism, generally designated 40, is provided at the end of heat exchanger 22 last left by the entering air and first entered by the leaving nitrogen. This includes four automatic check valves 4|, 42, 43 and 44. The lower end of course 223 has connected with it a conduit 45 which leads to the check valve 4|, and a branch 46 leads from the acme-1s conduit to the check valve 42.. A conduitdfl leads from course 226 to check valve 44, and .a branch 48 connects conduit 41., at a point between course 220 and the check valve '45, with the check valve 43. A conduit 49 connects the other side of check valve 43' with a conduit Ell leading from the check valve 4! to asuitable :restricter device 5i which createsa slight difference between the pressure in the conduit and the pressure beyond the device t l, the latter pressure being on the order of 2 pounds less than the pressure in conduit 56. A conduit 52 connects the conduit 5% the bottom of course 2213. A conduit 53 leads from the side of check valve 44 opposite the conduit 4! to the outermost course of the heat exchanger 23. Nitrogen always flows outwardly through conduit 53. A conduit connects the side of check valve 52' opposite the conduit "46 to theconduit 53. Each of the check valves 4! 42, 4'3 and opens in the direction indicated by its and prevents opposite flow.

The res'trictor 54 is connected, as at '58, to a chamber 51 within the top of an evaporatorcondenser '68 having a suitably insulated casing 6! and having in said casing an oxygen conducting conduit or course 62 and an air con ducting conduit or course '63 in close heat exchange relation with each other. The conduit or course 63 is connected at '54 with the chamber 51. The oxygen conduit or course 5 2 is connected by a conduit with the bottom of course 22A of exchanger 22. The top of course 229 of exchanger '22 is connected by a conduit lit with a conduit 6! leading from the-chamber "5'1, and the .re-united stream of air passes to a-conduit Til which leads to the expansion engine 13 later more fully described.

When the air entering the system is passing through course 22B it flows past the check valve 41.. When course 22B is serving for outflow of nitrogen, the nitrogen flows from conduit 53 through conduit I55 and past check valve t2 and through conduits llfiand 45 to course 2218. When course 22C is serving for inflow of air, entering air flows past the check valve 43. When course 220 is being used to conduct leaving nitrogen, the nitrogen flows past check'va'lve 't' tand through conduit 41. As the entering air is at a much higher pressure than the leaving nitrogen, no

check valve subjected on its discharge side to air can be opened by the lower nitrogen pressure.

The heat exchangers 23 and 24 have been previously mentioned. The exchanger 23 has four courses: a central one 23A, a next course 23B, a third course 23C, and an outer course 2313 surrounding, as shown on the drawings, course 230. The exchanger' l has, as shown, a central course MA, an outer course 240, andan intermediate course 2313. It-will of .course be un'den stood that the several courses are in good heat exchange relation with respect to each other.

The connection of conduit 53 is with the top of the outermost course 23D of exchanger 23. The bottom of coursei23D isconnected-by a conduit 68 with the bottom of course 240 of exchanger 24, and the top of course "240 is connected by a conduit ll with-a nitrogen outlet (the efliux connection) 12 of a single column F3. The internal construction of this column and certain special adjuncts associated with it will be described after the general system has been considered as a whole. The compressed air course-53 of the evaporatormondenser E9 is connected by :a conduit 14 with the top of course 2'33 of exchanger 2:3. The bottom or this last course :is connected by a conduit l5 with-a valve device 16 which, in the particular apparatus shown, and when the latter is :used for oxygen production, is adjusted 'to effect a pressure :drop betweenfits opposite sides on the order of 88 p..s.;i. for a compressor delivery pressure of 160 p s'. This is substantially the same reductionin pressurezasr occurs in the expansion engine [8 later described, when the latter is operating with its longer period of admission hereafter more fully explained. The downstream side of valve device 66 is connected with a conduit 11 which. leads to a condenser coil or element til. in the lower end of the column .73. The central course 23A of exchanger 23 is connected at its top witha conduit 19 leading to the oxygen course 62 of the evaporator-condenser16B, while the bottom of the course 23A is connected with the bottom of the central course 24A of. exchanger 24 by a conduit 80. .A conduit 8| leads from the top of the central course :24A and is connected with the discharge of a liquid oxygen pump later described. The condenser unit '78 is connected at its other end itfrom the conduit 11) by a conduit 82 with the intermediate course 2413 of exchanger "24-. The 13013 .01 course 243 is connected with a conduit 83, of which more will shortly 'be said.

The remaining course .230 of exchanger 23 is connected at its top with an expanded air conduit 85,.and its lower end is connected by :a conduit 86 with a check valve 81 openable towards the conduit Hand connected with the latter by a connection 88. The check valve '81 opens toward the conduit H, but only when the pressure in the conduit 86 is sufiicient'to effect opening of check valves! against the pressure in conduit '11.

"The expansionengine 18, which maybe at the construction shown in the co-pending Samuel C. Collins application Serial No. 665206, filed April 26, 1945, and now Patent No. 2,607,322 provided with suitable-means for predeterminedl-y lengthening andshorten-ing the period of admission, or which maybe of 'thecharacter-of the expansion engine employing cam follower rollers one or both :of which coact with a cam depending on whether early or late out-on is desired, which expansion engine is illustrated and described in an application of Win W. P aget, Serial 'No. 31;17, filed June 4, 1948, now Patent No. 2 ,638,923,May 19, 1953, or-of other suitable construction, includes a cylinder having admission and exhaust valves, not shown, and to the admission'valve :of which air under pressure is admitted from the conduit "is through a conduit 9! with whichan In surge tanlrSE is connected so as to minimize fluctuations in flow. A discharge or exhaust connection '93 leads from the expansion engine to a. Discharge surge tank 94 which have associated with it a strainer to catch any snow which might otherwise-attain to the column while the heat exchangers 2t and 22 .werenotfully cooled down during the starting of the apparatus. The expansion engine supports sonthe top of its cylinder a jacketed liquid cxygenpump SEE-of any suitable construction, the liquid oxygen pump being, for example, actuated by the expansion engine piston, as is the pump shown in the last above mentioned application of 'Win'W. Paget, or'in an other suitable manner. The conduit BI is connected with the discharge of the liquid oxygen pump 95 while this pump has a suction connection 98 leading to it from a strainer 9.? which is cooled oriachetedby' liquid "air, the jacket herein being represented by a coil 98. To the strainer 91 a conduit I leads from the evaporator-condenser at the bottom of the column I3, the conduit I00 communicating with the condenser-unit-enclosing chamber I0! in the bottom of the column at a point at the desired liquid oxygen level in the latter.

The Discharge surge chamber 94 has connected with it a conduit I which is connected to a valve structure I06, which valve structure includes a passage or chamber I0! continuously in communication with the conduit 85 and another chamber I0I connected through a conduit I09 with the interior of the column at a point spaced an appropriate distance from the top of the latter. The valve structure I08, which may be called a by-pass valve is adapted to have the two chambers mentioned connected in communication with each other and thus to connect the Discharge surge chamber 94 in free communication with the upper part of the column through the conduit I05, valve structure I08 and conduit I09. In the drawing, the constant communication between the conduits I05 and 85 is indicated by the passage or chamber I01, and the communicability of the passage or chamber ID! with the conduit I09 is indicated by the valve I08. Details of valve I06 can be better understood by reference to Patent 2,588,656 to Win W. Paget.

The expansion engine I8 is provided with valve gear adapted to permit the engine to operate with admission for a relatively short portion of its working stroke or with admission for a considerably larger portion of its working stroke. When cutofi" is relatively late in the working stroke, the valve structure 06 will prevent communication between the Discharge surge chamber 94 and the column through the conduit I09; and when communication between the Discharge surge chamber 94 and the column is effected by the appropriate adjustment of the valve structure I90, the expansion engine will be operated with admission for said relatively short portion of its working stroke. Various means may be provided for effecting the desired changes in period of admission of the expansion engine, as for example, with a camopened admission valve as shown in the Samuel (J. Collins Patent No. 2,607,322, the provision of selectively operable cams with different dwells, or cams one relatively adjustable with respect to the other, or cam follower rollers one or both cooperating with the cam depending upon whether early or later cutoff is desired, may be employed, as in the apparatus of the Paget expansion engine application.

Only such air will flow through the evaporator-condenser 60 as cannot pass through the expansion engine. When the latter is operating with relatively late cutoff, complete condensation of the fraction of the entering air which passes through the air course 63 of the evaporator-condenser 60 may conceivably be efiected, but if more air passes through this course than can be condensed by the available cold provided by evaporation of liquid oxygen in the course 62 of the evaporator-condenser 60, at the pressure (on the order of 50 p. s. i.) which then exists in that course, the excess unliquefied air will be condensed in evaporator-condenser I8.

The conduit 83, previously mentioned, leads to a valve device IIO which is adapted to be ad justed to efiect a reduction on the order of 60 p. s. i. in the pressure of the fluid (liquid air) which flows through it; and the downstream side of the valve device I I0 is connected by a conduit III with the jacket 98 for the strainer 91; and the top of this jacket is connected by a conduit II2 with a jacket H3 of the liquid oxygen pump 95, there being a conduit II4 leading from the jacket II3 to a connection II5 through which liquid air may be admitted to the top of the column 13.

The column I3 may be of any suitable construction, and is illustrated as of the conventional packed type. Of whatever type it may be, it will provide a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact.

The column may normally be operated with. a pressure on the order of 6 or 7 p. s. i., and in order to evaporate liquid oxygen with the latent heat of condensation of air under pressure in the condenser I8, the pressure of the air in said condenser should be on the order of 70 p. s. i., and accordingly the valve IIO will be set to maintain a difierential in pressure of about 60 p. s. i. between its upstream and downstream sides, the downstream side being substantially at column pressure, and the upstream side substantially at a pressure of '70 p. s. i. The expansion engine, when working with the later cutoif, has an expansion through it at least substantially equal to the difierence between 158 p. s. i., the pressure in line I0, and the pressure in the line 'II. Thus the expansion engine provides a pressure drop on the order of 88 p. s. i. This 88 p. s. 1. drop, plus the '70 p. s. i. pressure previously mentioned, plus the differential in pressure of about 2 p. s. i. provided by the resistor 5|, gives a cumulative pressure of 160 p. s. i.; and that is the pressure at which the two-stage compressor, not shown, which delivers air to the conduit II, may deliver air continuously. It is to be noted that the conduit I5 and valve device I6 are substantially in parallel with the expansion engine and the check valve 81, and accordingly the valve device I6 is set to give a pressure reduction on the order of 88 p. s. i., so that the air starting at 158 p. s. i. in the chamber 5! and passing through the air course 63, conduit '14, heat exchanger course 23B, conduit I5 and past valve device I6 may attain to the pipe 11 at substantially the pressure at which the air is delivered through the conduit 88. Thus, it may be observed that the sum of the column pressure, plus the reduction in pressure at the valve device H0, plus the pressure reduction across the valve device it, plus the 2 p. s. i. drop through the resistor 5i and plus the resistance in various conduits also equals 160 p. s. i., the delivery pressure of the compressor supplying compressed air to the conduit II.

The apparatus, we may call it a generator,-

may be operated to provide oxygen at relatively low pressures, say on the order of 50 p. s. i. and at relatively high pressures,.say on the order of 2000 p. s. i.

Regardless of which system of operation may be in use, liquid oxygen drawn from the cham-- ber I OI in the column I3 through conduit I00, the strainer 91, and conduit 96, is pumped by the liquid oxygen pump through the conduit 8i, through the course 24A of heat exchanger 24, through the conduit 80, the course 23A of heat exchanger 23, conduit I9, the oxygen course 62 of the evaporator-condenser 60, the conduit 65, course 22A of heat exchanger 22, conduit 33, and the course 2IA of the heat exchanger acme-rs ll, and-"finally #is delivered at the desired .ter- :minal pressure through the: pro duct delivery 1 pipe S. And-the nitrogen leavingthe-column byway of the connection J2 passes through-the conduit TH, ithrough course 240 .of heat exchanger :24, through conduit 68, through --course 2 SD- of heat exchanger 23, through conduit =53,=through one or the other of thecourses 2-213-- or "2-2C of heat exchanger 22, throughpne or the other of the "conduitstl .or 32, through one or-the otherof vthe courses 2H3 or 21C of heatexchanger 2|, through one 1 or .the -other of the conduits 45-01: 15, and through the escape 13, having passed through appropriate passage means in the valve :mechanism =t2. Thus it will-be evident-that the streams of oxygen and nitrogenpassing through *theiheat exchangers Z2 and 2 I will cause'carbon dioxide and Water vapor in the entering -air stream,-supplied'perhapeat -300K.'- and 15010. s. i., to be:condensed, or condensed-and frozen, 'on the Walls of the passages in these exchangers through which the entering air may at any given :moment he flowing, and that liquid "water willbeevaporated or-entrained, and deposits of ice .'-'and carbon dioxide 'snoW-sublirned, and be carried :out, by the leaving nitrogen stream, 'of the: passages in -which they have been deposited. A- portionof the-air which-ispassed throughthe heat exchangers 21 and 2-2 is caused to pass again 'through-theheat exchanger 2-2, through a course 221 thereof, aspreviously explained,-flowing -through the conduit "52, course 22D, and conduit 65 and rejoining the main mass of-air which. passes, during theproduction' of low pressure :oxygen, through the chamber 57 and 'conduit 61 and the reunited streams pass through the conduit and the conduit "9| into the expansion engine to be expanded therein and to be'cooledby the performance'of-Workduring the adiabatic expansionof thefiuidin the expansion engine. The 'flovv through-conduit 52, coursei. 2D of :heat exchanger 22, and conduit'iiii caused by the device !i,=which provides approximately a 2-=poun'd difference in pressure at its opposite sides.

iDuring the production "of "oxygen at 50p. s. ji., about 312% of the *total mass of entering air passes :through the air course 63 of evaporatorcondenser 60 inheat exchangerelation with the leaving oxygen product. '-When oxygen atZQOO p. s. :ixisthe desired product, as much as 60% of-all the air may pass through the air course 63 of evaporator-condenser 60. The "air which leaves i the-heat exchanger 2-2 on its way to pass throughfthe chamber 5! of evaporator-condenser iiiliand fiow through the" conduit 6'! is at .a temperature of 115 K. and a pressure of "160 p. s.,i. gauge. Atthe downstream side of the restrictor device-'5'! the pressure is 158p. s.-i. gauge. The recirculatedair whichfiows through the conduit 661is at a pressure of on the order of 158p. "sui. andatemperatureof-'18()--K. just before it joins the fluid streamin conduit 61. Whenthe streams have been mingled in the conduit 10, all theair is at.'a temperature of 135-K. and a pressure of 158 p. s. i. The portion of the air whichfiows through the conduit 10 and ;does Work in the expansion engine leaves the latter at a temperature of l10 K.'and-a pressureofi'lop. s. i. when 50-pound oxygen-is to'be produced. This expanded air passes through the conduit 85, through-course 23C 01" heat exchanger 23, and emergesata temperature-of 105 'K. and a pressure of 12 70 :p. s. 11. gauge, and-passes the check valve zfllito mix iwith liquid air which has passed 'the valve device 16, andithereiisrformedastream -partially=of liquid air and partially :of expanded air-at a temperature'of K..-an d.a pressurelof '70 p. s. i. 'll he air ifromatheaircoursesfiii :of the I evaporator condenser :69 l emerges sfrom heat exchanger 23 and enters .the [conduit 15 :at .a temperature of 112" :-K..-and ;a pressure .of 2158 :p. s. i. After:passingrthroughithe .y-alvmdevice E6 andundergoinga drop in-pressure-ofabouti'88 p..-s.ii., 'the liquid air .isat the :same pressure as the expanded-air.coming-rthrough=conduiti86.

The 'mixture of liquid. air andzexpanded zaircat :a temperature of 1100" .and a pressure .of p. s. vi. enter ithe condenser coil :7 8 .and lie condensed .by :reason :of thegiving up io'f heat in the process of vaporizing oxygen inithefloottom of the column. The liquid air :emerging from thecondenser .18 is ataitemperature of 96K. :and apressureof .70 p..s..i.,.and. after this liquid air has .passed the :valve device I!) .and its pressure .reduced :by :approximately #60 -p. s. i the "liquid air will be at a temperature --of 83 K.--and a pressure'ofabout -9 -p. s. i.,hav-ing in mind friction losses in the passages. Following the jacketing of the oxygen strainer 91 and the liquid oxygen pump $5, the still liquid air will enter-the top ofthe column-at atemperature of 83 K.and-apressure of perhaps 7 p. s. i taking into consideration friction :losses, :and fit will the rectified inthe. column so 1that substantiallypure oxygen (99,5 pure, at;least) ,canhe drawn from an appropriate point in the evaporator.condenser arrangedinthe bottom (If- .13118 column at.a temperature .of J9,5 K. and a pressure of! p. ,s.ji. Thisjiquid .oxygemwilhflow through ,the strainer =Q'I',,CQI1duit 96, ,the liquid oxygenpurnp c5, .the=cond11it .8 l and v.thecentral courses, ,in series, lof heat ,exchanger .24, heat exchangerlt, evaporatorecondenserAil), heatrexchanger 2.2,. and heat exchanger #2:! and emerge, when .50 pound .oxygen :is fleeing produced, in the ,formvofg aseous:oxygenvat the;mfiuth;of;the product pipes.

W en zo ygen at; relativelythigh pressure, say at za-gpressure ;s.uited :for icylinder charging, a is 5150 be .produced,;the .valverstructure H1 6 Will be. operated ;.to connect the conduits W5 and 1 09 and the expanded lair leaving :the .expansion engine Will thenpass i;through the conduit 1135; the valve structure 1 Hi6, .and the :conduit M9 into the column,.;and zthe pressure of ithe air in the conduit I 65 .ZW'illi be reduced substantially to that within theuQo-lumn, and. accordingly no more expanded air .Will :be. discharged through thechelcvalve 81, because :this valve will Joe held closed by the ;pressure, lOnJth-e order of "70 p.--s. -i., which subsists inxthe conduit fl 'i. :At the'time thevalve structure amt .zis operated #to permit theexhaust from zthe =expansion :engine to pass substantially directly into; the. column through the-condu-it H19, the ipoint rof cutoff :of i the expansion engine =F8 will :be changed "to make it :much earlier in the stroke; sand, it-he speed of sthe expansion engine remaining lunaltered, .much less-roughly ha-lfas muchail can ,.;-go :;.through :the expansion engine. jesza result of ithis, .the:air which-cannot flow throu h :the ;c.onduit $567 and be :passed through :the :expansion engine will :of necessity gorthrough the. air-'course 63 of evaporator-condenser 1:60, and, "having passed through course 23B of heat exchanger -23jthis now-much larger mass -of air, perhaps 60% ,of the:total,m&. will passthrough the valve. device T6 and ,enterthe con'densercoihlfi of-the evaporator-condenser at 1 1 the bottom of the column I3 and be liquefied therein. This larger volume could not be liquefied in the evaporator-condenser 68 and the heat exchanger 23 because the oxygen now at a much higher pressure cannot be vaporized at the temperature of condenseing air. The reduced volume of liquid air from condenser coil 18 will pass through the heat exchanger 24 by way of course 24B and next pass through conduit 83 and the valve device H8 and then, after jacketing the strainer 91 and the liquid oxygen pump 95, will be passed into the top of the column for rectification. A much smaller percentage of the total oxygen content of the air entering the apparatus will be delivered during the production of 2000-pound oxygen than during the production of 50-pound oxygen. The foregoing description of the modes of operation of the generator are probably more than adequate as a basis for an understanding of our invention which will now be described, but should further details be desired they will be available in the patent to be issued upon the application of the applicant Collins, Serial No. 383,541, hereinabove referred to.

As previously indicated, we have 'found that the quality of the oxygen product may be substantially improved, when necessary, by returning a portion of the product to the bottom of the column. For this purpose we have provided, according to the illustrative embodiments of the invention in its apparatus aspect arrangements as follows:

The column is provided with a tapered perforated element or screen C of conical shape arranged at the bottom of its packed space and disposed with the apex of the cone downward. The product line S has a branch II5 equipped with a pressure reducing valve II6 adapted to maintain at its output side a predetermined pressure. A pressure on the order of five pounds above column pressure is suitable. This pressure reducing valve delivers relatively warm gaseous oxygen to a conduit III, which leads to a valve mechanism generally designated II8. Two possible forms of such a valve mechanism are illustrated, the preferred form shown in Figs. 1 and 2. The valve mechanism H8 (or H8) is adapted to effect, when this is desirable, connection of the conduit II! with a conduit H9 opening at I28 through the bottom of the column beneath the level of the liquid oxygen therein. It is desirable to control the introduction of oxygen to the bottom of the column automatically in accordance with the purity of the product being formed.

Secured to the inverted cone C, as by legs I23, herein shown as four in number, is a dish-like element I25 to which there is connected a nearly annular bulb I26. In this bulb there is a quantity of a liquid the variations in the saturated vapor pressures of which are to be used to effect the desired automatic control. In the case of oxygen production, the bulb may be filled either with at least substantially pure liquid oxygen and its saturated vapor or may contain in liquid and saturated vapor form a quantity of oxygen of somewhat less purity than the purity of the desired oxygen product. In both cases it will be noted that the bulb contains a substance relatively close in constitution to the constitution of the desired product. The bulb I26 is connected by a tube I28 with a passage I29 in the valve mechanism II8, as at I30. Further details of this passage I29 and its relation to the valve mechanism will be later given. Another conduit I3 I, having an open mouth I32 within the column just below the bulb I26 is connected also with the valve mechanism H8 at I33. The open end I32 is downwardly directed as at I34 in order that liquid oxygen may not, as would perhaps be the case were it inverted from the position shown, tend to enter the mouth of the tube I3I and flow into the valve mechanism I I8.

The valve mechanism II8 (as does also the simpler valve mechanism 8' of Fig. 5) includes a casin I35 provided with a bellows chamber I36, and a bore I3! formed in the upper part of the casing I35 opens at its lower end into the chamber E36 and is arranged coaxially with the chamber. Within the bore I37 there is mounted a valve block I38 which has threads I38 at its upper end engaging with threads I48 formed in a projecting neck-like portion I42 on the casing I35. A head I43 is provided on the valve block I38 for permitting adjustment of the latter in the bore The valve block I38 is provided with a plurality of grooves in its periphery. These include relatively remote grooves I45 and I46 whose primary function is that of improving sealing. To that end they contain 0 rings 0. There are other spaced grooves I48 and I49 formed in the valve block, these, like the first grooves, being annular grooves, and being disposed between the grooves I45 and I46. Between the grooves I48 and I49 is another sealing groove I56 also provided with an 0 ring 0. The grooves I48 and I49 communicate with each other through the formation in the valve block of diametrically extending passages I5I and I52, connected with each other by an axial passage I54. The passage I5I at its opposite ends opens into the groove I48, and the passage I52, at its opposite ends, opens into the groove I49. The axial passage I54 has an enlargement I55 at its lower end, and communicates at its upper end with the diametric passage I5I, and at its lower end with the diametric passage I52, through the enlargement I55. A needle-type valve element I 51, having a conical end I58 adapted to cooperate with a circular seat I59 formed at the upper end of the enlargement I55, may seal off communication between the grooves I48 and I 49, or permit variable communication between them. It may be noted, before describing control means for the valve I51, that the groove I48 is connectible, in the preferred embodiment of Fig. 2, by a further control valve mechanism I68, which will shortly be described in detail, and a passage I6I with the conduit II! (in Fig. 5 the connection is direct). The groove I49 is connected by a passage I62 with the conduit H9. Accordingly, when the valve element I5! moves downwardly there may be communication between the conduit II! and the bottom of the column. In the embodiment of Fig. 2 an auxiliary communication will be efiected which may much exceed in flow capacity the communication possible with the structure shown in Fig. 5.

The control for the valve I51 may now be.

noted.

Within the chamber I36 there is arran ed a bellows device I64. A so-called plug I65 is adapted to be suitably secured as by rivets I68 to a radially extending flange I61 formed on the lower end of the casing I35, a suitable spacer ring I68 being provided properly to locate the upper end of the plug I65. The plug is traversed by two longitudinally extending passages: the passage I29, previously mentioned, and a parallel :passage IfiQ-normallyclosedhy arplug I10. At :their uppenendsthe passages I29.and I69:com municateiwith adiametric passageway I1I opening intoanannular-groove I512 formed in the periphery of a reduced upwardlyzextending portion tl'iof the plugmember I 65. Surrounding this reducedportion 2 I13 is a sleeve member I15, having a radial portion! 15 at its lower endcarrying integrallywithit a threaded ring portion I11, whichengages threads t18'on the plug member The bellowsdevice 5 60 isappropriately secured in fluid tight relation, .as at I80, :to the radial portion I16 associated with the sleeve member :I' 15. The top ofthebellows I64 isv suitably secured, asat .182, in fluid tight relation to an annular memberlfltto whichthere-issecured a centralivalve supporting element l'M-havingan upwardly extending hollow sleeve-like "portion I85, within the bore I86 of which the-"lower end of the .valve element I'51 is received with slight clearance. The lowerend of the-valve element is rounded as at 1513. The sleeve like portion I85 is surrounded by a groove I90, in which a discontinuous resilient wire ring IOI is seated; and this ring has a radially-inwardly extending, transverse arm portion -I92,-which enters atransverse bore 193 in the valve I51 and engages the walliof 'thisbore about at the axis of the valve, and which is adapted, through the flexure of the radialarmuportion I9 2, to press the valve I51 against thebottom of the bore l8'6,.but to permit a slight uncentering of the valve relative to the bellows .IM, thereby avoiding cramping. The connection 133 opens through a conduit I95 into the chamber I35. As the connections of the bellows device IE4, at-I80 and I-82, are fluid tight, as above noted, it will be appreciated from the arrangements described'that the exterior of the bellows is subjected tothe pressure at the mouth I32of the conduit I3I, while the interior of the bellows is subjected to a pressure which varies with;the temperature of the fluid contained in the chamber of the bulb I26.

The control apparatusso'far described iscommon, with the exception noted, to the embodiments of Figs.'2and 5. It is allthatthe embodiment of-Fig. 5 includes andall that is requiredfor operativeness, but for the admission of larger amounts of oxygen back into the bottom of the column, the-control 460 previouslyreferred to is desirable. Referring, therefore, to Fig. 2, the construction andarrangement of this control are as follows:

A housing or casing 200 is provided in association with the casing I35. It *is hollow and contains a diaphragm 20I forming at the opposite sides'thereof chambers 202 and 203. A small passage 204 inthe diaphragm connects'the chambers202 and 203. A suitable connecting member2il5 connects-the housing 200 with the valve mechanism -I I8. A passage 206 in the connecting member 205 connects the chamber 203 with 'the passage -'i'6I. A spring 201 normally maintains the diaphragm against "a seat 208. The diaphragm has a plate 208V secured to it which acts as a valve in cooperation with the seat 208. A passage 20 9 leads from the-seat to a conduit2I0 which connects with the conduit '9 as by a "T connection 2. The conduit H1 is connected with a passage'2i2 which opens into the chamber 202.

In the embodiments ,of both Figs. '2 and 5. when the "bellows IB I moves the valve I51 from its seat, oxygen product flows 'from the conduit H1 tothe-con'duittIS. 'Thisflow, in the embodimentaof Fig. 5;;is directly regulatedfibyithemeedle valve 151. In the embodiment ;of1:Eig. 2, .the needle valve :l-51zcontrols1some :(at-yery slight) oxygen flow itself and: also-plays:arpilotiunction for the valve platez208V and its supporting :diaphragm. Substantially opening of thezvalveslfil causes arpressure dropin'the chamber 203 as the passagex204. isztoo smallito. deliver 218i muchaoxygen as the openvalve I'51 can-permit tozpassiit. The then greater .pressurefintthe :chamber 202 will thereforeimove the diaphragm' 20I against Lthe tension of thespring 201, moving the .valvei208V away .from the-seat :2 0 8, and allow oxygen :pro-d uct:toflow directly "from'the; conduit .I' I1 :through the .chamber .282, passage 209 andthe'conduit 21.0 to'the .conduit:I.I9 which'opens intozthebnttom of thecolumn beneaththelevel' of .theliquid oxygen therein.

It will :be understood that, if thesubstanceiin the .bulb I26 is oxygen of greaterRpurityIthan'Lthe oxygen product sought .for, the -.vapor pressure under-the bellows :[64-1Wi111b6 slightlyibelow the pressure in the column at I32 when the :liquid flowing over the bulb is of the desired v: purity, while, if the substance. in thebulb 126 ie-oxygen oiqlesspurity than theoxygenlproduct sought for, thevapor pressure within thelbellows' I64' wi1l be slightly greater than the pressure within --the column at E32 when the liquid :flowing over the bulb is of the desired purity. .nccordinglvthe element I 38 will be adjusted in the firs't case further inward than in .thersecond :case, because in the first case the bellows :will be slightly: axially shorter thanin the second iwhen the valve 151 is just held .against .its seat (with sutficient pres-' sure to resist the pressureof the oxygen in petssage I55. .In both cases however, whenthe temperature of:the liquid flowing over thebulb 425 is reduced, as occurs when its purity falls below desired product purity, -the pressure :within the bellows 64 will be so reduced as to effect oxygen admission to the :column .because the pressure within the conduit I.-3I vand outside of the bellows I 5 3 does not vary materially as thepressure within the bulb I25 :does. Thus a decrease in the purity of the oxygen'inthebottom of thecolumn is as it were anticipated, and the valve I51 is movedfrom .itsseatand, in the embodiment of Fig. .5, allows oxygen product to flow through the .conduit 5;! t1, the groove I28, thediametric passage I152, the axial passage I54, theenlargement I55,-the diametric passage I52, the annular groove #49, the passage I62 and the conduit -II9 into the liquid oxygen .in the bottom of the 'column, entering the latter at I20, as previously noted .the pressure reducing valve I I6 being'set so as to provide a pressure in the conduit '1 just slightly exceeding'the sum of the desired column pressure and the .head of the'liquid-oxygen.

With the construction illustrated in Fig. 2 downward movement of :the valve 451 from its seat results, as; previously notedpin the-provision of an opportunity for oxygen to-fl'owfromthe chamber 203 through :the passages 256, 6 i I5 I I54, I52 and IE2, and the conduit I=F9,-into "the bottom .oithecolumn. The flow capacity will normally quickly exceedthe potential-rateof'flow of oxygen .from the chamber 202 through the restrictedpassage 204-to the chamber 203. Thus the pressure at the left-hand side of the diaphragm 25 would be less than exists at the right-hand of thisdiaphragm and the valve plate 208V will be raised from the seat 208, .thusipermitting the flow. of a-substantial guantityiof :IBlatively warm oxygen from the conduit 1 I1 through the passage 2| 2, the chamber 202, the passage 209, the conduit 2H! and the conduit I [9 into the bottom of the column. This arrangement provides for a greater range of control of oxygen purity. When the oxygen dripping into the dishlike element I improves in percentage of purity the temperature will increase and this will be attended by increase in the pressure inside the bellows 64 and the closing of the valve [51. In the form of the invention illustrated in Fig. 5 this will directly reduce or entirely shut 01?, as the case may be, the flow of oxygen to the bottom of the column and, in the form of Fig. 2 it will result in an appropriate control of the position of the diaphragm 20l and the valve plate 268V and the resultant control of the volume of oxygen passing into the bottom of the column.

It will be clear that the quantity of oxygen product admitted to the bottom of the column may vary from none at all to a substantial amount, depending on the operating conditions, and the quantity will be regulated and controlled automatically by the mechanism which has been described.

It will be observed that we have provided an improved method and two improved physical embodiments of apparatus for improving and automatically controlling the purity of the oxygen produced by a generator. The improvement effected is a definite one and it may be accomplished without the necessity for frequent intervention of an attendant.

It will be understood that our invention is not limited to the improvement of oxygen purity, but with suitable adaptation and with the substitution in the bulb of a quantity in substantially pure form of the product whose purity is to be controlled, it may be used in other rectification processes. By substantially pure form we intend to include not only substantially chemically pure substances, but to cover broadly the concept of substantial identity in constitution with the product desired, even though the latter itself be a mixture. Substantially pure form is also intended to cover not only a condition of slightly greater purity than the purity of product desired, but also a condition of slightly lower purity than that desired for the product. Moreover, it is not limited in its broader aspects to introduction of the warmer vapor below the level of the liquid product in the column or even to the introduction of a vapor at a higher temperature than subsists at its point of introduction.

While there are in this application specifically described two physical embodiments which the r invention may assume in practice from its apparatus aspect and by which its method aspect may be practiced, it will be understood that these are disclosed for purposes of illustration and that the invention may be modified and embodied and practiced in various other forms and ways without departing from its spirit or the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent is:

l. The method of maintaining the purity of a product of rectification in a column, which includes withdrawing the product in a liquid state from the column, mechanically increasing the pressure of the withdrawn product while in the liquid state, vaporizing and warming the withdrawn product through heat exchange with a mixture of which the product is one component, which mixture is on the way to the column for rectification therein, and the return to a point 16 in the column below the liquid level of such product in the column of a quantity of such product in its gaseous state and at an at least slightly higher pressure than the pressure in said column at such point of return.

2. The method of maintaining the purity of a product of rectification in a packed column which includes the return to a point in the column below the liquid level of such product in the column of a quantity of such product having a higher heat content per unit of mass than does said product in the column and at an at least slightly higher pressure than the pressure in said column at such point of return and the control of the quantity of such product so returned by the temperature of the product in liquid state at the completion of its passage through the column packing and above the liquid level of such product in the column.

3. The method of improving the purity of a product of rectification in a packed column which includes the return to a point in the column below the liquid level of such product in the column of a quantity of uch product in its gaseous state and at an at least slightly higher pressure than the pressure in said column at such point of return and the control of the quantity of such product so returned by the temperature of the product in liquid state at the completion of its passage through the column packing and above the liquid level of such product in the column.

4. The method of maintaining the purity of a product 01 rectification in a column, which includes withdrawing the product in a liquid state from the column, mechanically increasing the pressure of the withdrawn product while in the liquid state, vaporizing and warming the withdrawn product through heat exchange with a mixture of which the product is one component, which mixture is on the way to the column for rectification therein, and the delivery to a point in the column, below the liquid level of such product in the column, of a quantity of such product at a higher temperature and at an at least slightly higher pressure than the pressure in said column at the point of introduction of such product into the column. I

5. The method of maintaining the purity of a product of rectification in a column, which includes withdrawing the product in a liquid state from the column, mechanically increasing the pressure of the withdrawn product while in the liquid state, vaporizing and warming the withdrawn product through heat exchange with a mixture of which the product is one component, which mixture is on the way to the column for rectification therein, and the delivery to a point in the column, below the liquid level of such product in the column, of a quantity of such product in the gaseous state and at a higher temperature and at an at least slightly higher pressure than the pressure in said column at the point of introduction of such product into the column.

6. A method of producing oxygen of a preselected purity including compressing, cooling and liquefying air and rectifying it in a column at a relatively low temperature and reduced pressure thereby producing a liquid oxygen product and a nitrogen-rich effluent, and when the temperature of the oxygen reflux is reduced due to a falling ofi in purity of such reflux, utilizing such reduction in temperature applied as a control at a point above the liquid oxygen product level to 17 effect a return of a controlled quantity of oxygen product to the bottom of the column.

'7. In a procedure in which a stream of relatively pure oxygen in liquid form is withdrawn, following an air fractionating operation, from a liquid pool in a rectifying column, has a pressure mechanically imposed upon it, and is vaporized and warmed through heat exchange with a stream of air en route to separation, the steps for raising the purity of the oxygen product when it falls below a desired value which include withdrawing oxygen vapor so warmed from a stream of oxygen product, and delivering, under the control of the temperature of the oxygen product in liquid form in the rectifying column before it enters such pool, variable quantities of the warmed oxygen vapor to such a liquid pool below the surface thereof.

8. In a procedure in which a stream of relatively pure oxygen in liquid form is withdrawn, following an air fractionating operation, from a liquid pool in a rectifying column, has an increase in pressure mechanically imposed upon it, and is vaporized through heat exchange with a stream of air en route to separation, the steps for raising the purity of the oxygen product when it falls below a desired value which include withdrawing oxygen vapor from a stream of oxygen product, delivering variable quantities of the warmed oxygen vapor to such a liquid pool below the surface thereof and controlling the quantity of oxygen product so delivered by the variations in the purity of the oxygen reflux above such pool.

9. In combination, in a gas separation apparatus, a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part or such means a collecting space for a liquid, relatively pure product of the rectification process performed within said column, means for withdrawing such relatively pure product from said collecting space, means for vaporizing the same and for making the same available in the gaseous state at a pressure exceeding the pressure within said column and at a temperature higher than the temperature of said product in said collecting space, means for conducting some of said product into said collecting spac at a point therein below the top of the liquid standing therein, and means for controlling the quantity of said product conducted into said collecting space including a valve having controlling means responsive to the temperature of the descending stream of liquid as it reaches the bottom of said first mentioned means.

10. In combination, in a gas separation apparatus, a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part of such means a collecting space for a liquid, relatively pure product of the rectification process performed within said column, means for withdrawing such relatively pure product from said collecting space, means for vaporizing the same and for making the same available in the gaseous state at a pressure exceeding the pressure within said column and at a temperature higher than the temperature of said product in said collecting space, means for conducting some of said product into said collecting space at a point therein below the top of the liquid standing therein, and means for controlling the quantity of said product conducted into said collecting space including a valve having controlling means responsive to the temperature of the descending stream of liquid as it reaches the bottom of said first mentioned means and including a bellows device and means for subjecting the latter on its opposite sides to the pressure above the liquid in said collecting space and to the vapor pressure of the pure product at the temperature of said descending stream of liquid at the point stated.

11. In combination, in an air separation apparatus, a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part of such means a collecting space for relatively pure liquid oxygen, means for withdrawing such relatively pure liquid oxygen from said collecting space, means for vaporizing the same and for making the same available in the gaseous state at a pressure exceeding the pressure within said column and at a temperature higher than the temperature of said liquid oxygen in said collecting space, and means for improving the purity of said relatively pure liquid oxygen including means for supplying not less pure and warmer gaseous oxygen into said collecting space at a, point therein below the top of the liquid standing therein, and means for controlling the quantity of said gaseous oxygen conducted into said collecting space including a valve having controlling means including an oxygen filled bulb disposed in said collecting space above the liquid level therein and responsive to the temperature of the descending stream of liquid as it reaches the bottom of said first mentioned means.

12. In combination, in an air separation apparatus, a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part of such means a collecting space for relatively pure liquid oxygen, means for withdrawing such relatively pure liquid oxygen from said collecting space, means for vaporizing the same and for making the same available in the gaseous state at a pressure exceeding the pressure within said column and at a temperature higher than the temperature of said liquid oxygen in said collecting space, and means for imp-roving the purity of said relatively pure liquid oxygen including means for supplying not less pure and warmer gaseous oxygen into said collecting space at a point therein below the top of the liquid standing therein, and means for controlling the quantity of said gaseous oxygen conducted into said collecting space including a valve having controlling means including an oxygen filled bulb disposed in said collecting space above the liquid level therein, and means for efifecting the flow over the same of the descending stream of liquid as it reaches the bottom of said first mentioned means.

13. In an air separation apparatus which includes a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part of such means a collecting space for relatively pure liquid oxygen, and means for efiecting delivery for use of such relatively pure oxygen from said collecting space, means for improving the purity of the oxygen product including means for introducing oxygen in gaseous form into said collecting space at a point therein below the top of the liquid oxygen therein and means for regulating the quantity of oxygen introduced includ- 19 ing a control valve andcontrolling nieanstherefor governed by thetem'perature of the descending stream of liquid as it reaches said collecting pfiC H c .7

14.- In an air separationapparatus whichincludes a columncontaining means for providing a large cumulative surface area at which a rising current of a gas and a descending streani of liquid may interact, and having belowthe lcwest part of such means acollecting space for relatively pure liquid oxygen, and means for effecting delivery for use of such relativelypure oxygen from said collecting space, means for improving the purity of the oxygen product including means for introducing oxygen in gaseous form and at a higher temperature than said relatively pure oxygen in said collecting space into saidcolleeting space at a point therein below the top of theliquid oxygen therein and means folregulating the quantity of oxygen introduced including acontrol valveand controlling means therefor; including a further valve governed by the; temperature of the descending stream of liquid as it reaches said collecting space. i

15; In an; air separation apparatus which includes a column containing means for providing a large cumulativesurface area at which a rising current of a gas and a descending stream of liquid may interact, and having below the lowest part of such means a collecting space for relatively pure liquid oxygen, and means for eifecting delivery fo use of suchrelatively pure oxygen froinsaid collecting space, means folimproving the purity cf the oxygen product including means for introducing o rygen in gaseous form and at a. higher temperature than said relatively pure oigygen in said collectingspace into said collecting space at apoint therein below the to of the liquid ozg ygen thereinand means for regulating thequantity of oggygen introduced including a controlvalve having servo means for governing thepositionthereof including surfaces one constantly subiected tothepressure of the oxygen in gaseous fcrmand an opposedsurface subjected tcthe pressureof 'saidgaseous oxygen or a lower pressure and controllihg means for the pressure on saidlastrnentioned surface including a furewe ye aer ted brine. temperature of h descending stream of liquid as it reaches said 11l i 16. In combination, in a gas separation ap- Parana f =9 fim s n a meapns 9 ovi la rge c umulative surface area at which a rising current or a gas anda descendingstream of liquild niay interact, and having a collecting space for a liquid product of the rectification process performed within said colu'mn, means for withdrawing siren precast from said collecting space, means for vaporizing. the same and for making the same avaiiame in the gaseous state at a pressure exceeding the pressure within said column, means for conducting some of said prod uct into said column, and means for controlling the quantity of said product conducted into said column including a valve having controlling means responsive to the temperature of thedescending stream of liquid as it reaches the bottom of said first mentioned means and including a pressure responsive device having oppositely facing surfaces and means for subjecting said device on its oppositely facing surfaces to the pressure in said collecting space and tothe vapor pressure, at theteinperature ofsaid descending stream of liquid at the point stated, of the product substance in a form purer than desired productpurity.

17. In combination, in a gas separation apparatus, a column containing means for providing a large cumulative surface area at which a rising current of a gas and a descending stream of liquid may interact, and having a collecting space for a liquid product of the rectification process performed within said column, means for withdrawing such product from said collecting space, means for vaporizing the same and for making the same available the gaseous 'state at a pres sure exceeding the pressure within said column, means for conducting some of said product into said column, and means for controlling the quantity of said product conducted into said column including a valve having controlling means responsive to the temperature of the descending stream of liquid as it reaches the bottom of said first mentioned means and including a pressure responsive device having oppositely facing sur-- faces and means for subjecting said device on its oppositely facing surfaces to the pressure in said collecting space and to the vapor pressure, at the temperature or said descending stream of liquid at the point stated, of the product substance in a form less p'u're than desired product purity.

SAMUEL C. COLLINS. WIN W'. PAGET. LEWIS TYREE.

References Cited in the file of this patent UNITED sures PATENTS Number Name Date 967,105 Claude et 2.1. Aug. 9, 1910 1,951,840 Roberts 'et a1 Mar. 20, 1934 2,142,446 mm l Jan. 3, 1939 2,327,648 Houghland Afig. 24, 1943 2,360,463 Brown Oct. 17, 1944 2,499,043 Voorh'ees m Feb. 28, 1950 

